01/08/08

4

PD-60332

IR3821AMPbF

Pin Description

Pin Name

Description

1

Vsns

PGood sense pin. Use two external resistors to program the power

good threshold.

2

Fb

Inverting input to the error amplifier. This pin is connected directly to the

output of the regulator via resistor divider to set the output voltage and

provide feedback to the error amplifier.

3

Comp

Output of error amplifier.

4

AGnd

Signal ground for internal reference and control circuitry.

5

AGnd

Signal ground for internal reference and control circuitry.

6

SS/SD

Soft start / shutdown. This pin provides user programmable soft-start

function. Connect an external capacitor from this pin to signal ground

(AGnd) to set the start up time of the output voltage. The converter can

be shutdown by pulling this pin below 0.3V.

7

OCSet

Current limit set point. A resistor from this pin to SW pin will set the

current limit threshold.

8

V

CC

This pin provides biasing voltage for the internal blocks of the IC. It also

powers the low side driver. A minimum of 0.1uF, high frequency

capacitor must be connected from this pin to power ground (PGnd).

9

PGood

Power Good status pin. Output is open collector. Connect a pull up

resistor from this pin to Vcc.

10

PGnd

Power Ground. This pin serves as a separated ground for the MOSFET

drivers and should be connected to the system’s power ground plane.

11

SW

Switch node. This pin is connected to the output inductor

12

V

IN

Input voltage connection pin

13

HG

This pin is connected to the high side Mosfet gate. Connect a small

capacitor from this pin to switch node (SW).

14

V

C

This pin powers the high side driver and must be connected to a voltage

higher than input voltage. A minimum of 0.1uF high frequency capacitor

must be connected from this pin to the power ground (PGnd).

15

AGnd

Signal ground for internal reference and control circuitry.

Pins 4, 5 and 15 need to be connected together on system board.